Dimenhydrinate is a well-known therapeutic agent for the prevention or treatment of motion sickness. Like many drugs, however, in particular drugs containing amine or amido groups, it has a strong bitter taste. Without proper taste masking, dimenhydrinate and such drugs cannot be adapted into acceptable orally administrable forms, especially in the form of chewable tablets. Current taste masking techniques, including simple polymer coating of the drug substance, have not been entirely satisfactory for dimenhydrinate to achieve the desired degree of taste masking due to its appreciable solubility in both aqueous medium and various organic solvents. Therefore, solvents used in conventional coating processes often partially dissolve the drug and expose the drug substance on the surface of the preparation.
Recognizing the problems, the present invention is directed toward a taste-masking coating preparation for active medicaments which have the solubility profile as dimenhydrinate, i.e. the ability to dissolve in both organic solutions or aqueous medium in an appreciable extent. We have found that by using two appropriate coating layers such active medicaments can be substantially free from the unpleasant tastes.